Hannibal crabs swarming behavior

Pleuroncodes planipes, or red crabs, swarm like insects across the ocean floor in a coastal eastern tropical region of the Pacific near Panama. This swarming behavior, never before seen among red crabs, was filmed using submarine video and autonomous underwater vehicle (AUV) photographs.
Read the article: http://arstechnica.com/science/2016/04/massive-undersea-crab-swarm-caught-on-video-for-the-first-time/